Spring housing for die springs



Dec. 3, 1957 R GERHART ET A1. 2,815,200

SPRING HOUSING FOR DIE SPRINGS Filed Sept. 14, 1955 INV NTORS 2074716 er 47'? 77 074775 7', ga /Z472? United States Patent SPRING HOUSING FOR DIE SPRINGS Roland Gerhart and Roland T. Gerhart, Detroit, Mich.

Application September 14, 1955, Serial No. 534,340

4 Claims. (Cl. 267-1) The present invention relates to a spring housing for die springs and a die mechanism incorporating such housing.

In the dies employed in stamping and drawing sheet metal parts, it is customary to provide a die member pro- Vided with a spring-pressed die element which engages the periphery of the sheet metal part to be drawn or stamped and holds it against a mating die member during the drawing or stamping operation. In the operation of such dies, the member and element are held in spaced relation by a plurality of springs positioned in aligned recesses in the member and element so that the element first engages the sheet metal part and thereafter holds it while the member continues to move toward the element and operate on the central portion of the sheet metal part to perform a drawing or forming operation. Since very heavy holding pressures are required, a large number of heavy, highly stressed springs are usually employed in die sets of the type mentioned. Considerable diflic-ulty has been encountered as a result of breakage of these springs inasmuch as spring fragments find their way into the space between the two die elements and cause breakage of the dies or the press when the press is closed. This hazard is aggravated when, as is frequently the case, the member and element are required to come into face to face abutment at the end of the drawing operation in order to perform a coining operation. The damage to expensive dies and presses and the loss of machine production resulting from such spring breakage has been substantial.

In accordance with the present invention, the aforementioned difiiculties are overcome by positioning the die springs within individual cylindrical housings which will retain spring fragments in the event of breakage and thus protect the dies against damage.

The objects of the invention include the provision of a housing for the above purpose and also a preferred and improved form of housing which is telescopic in nature, and further to provide a housing design which will simplify and reduce the cost of forming spring recesses in die elements.

Another object of the invention is to provide an improved die construction incorporating the spring housings of the type mentioned.

In the drawings:

Figure l is a longitudinal section through one form of the spring housing;

Figure 2 is a transverse section taken on the line 2-2 of Figure 1;

Figure 3 is a fragmentary section through a portion of a die mechanism incorporating the spring-retaining housing, the spring and other features of the invention; and

Figure 4 is a fragmentary section showing a modified form of the spring housing construction.

Figure 3 of the drawings shows a fragmentary portion of a pair of die members 1 and 2 which are positioned in face to face relation and are secured together for relative movement toward and away from each other by means of a tubular guide 3 having enlarged head 4, the guide and head being fixed to the lower die member 2 by means of a cap screw 5. The guide 3 is slidable within a cylindrical bore 6 formed in the die member 1, and head 4 slides within an enlarged countersunk bore 7 aligned with the axis of the bore 6. As a result of this construction, the die members 1 and 2 may move toward and away from each other within the limits permitted by the distance between the underside of the head 4 and the bottom of the countersunk bore 7.

The mechanism so far described performs part of a conventional die mechanism of the type in which the die member 1 is fixed to one element of the press, and the die member 2 is normally held in spaced relation to the member 1 by means of springs. As the die closes, the member 2 first engages the periphery of the work and holds it against a mating die member, not shown, while the die member 1 continues to move downwardly and perform a drawing or forming operation. In such die sets, a plurality of guides corresponding to the tubular guide 3 and a plurality of springs are normally employed, the number depending upon the size of the die and the nature of the operation. The die members 1 and 2 are illustrated in the drawing in their fully closed position in which the die member 1 solidly abuts against die member 2.

In dies of the above described type, it is customary to position the springs in aligned recesses in the die members, which recesses are similar to the blind, cylindrical recess 8 shown in the die member 2 in Figure 3. In accordance with the present invention the problem of machining the aligned recesses in the mating die members 1 and 2 is greatly simplified by clamping the two die members together and then drilling an opening entirely through the die member 1 and into the die member 2 thus forming a cylindrical opening 9 extending through the die member 1 and the blind opening 8 in the die member 2. The upper end of the opening 9 is countersunk to provide an enlarged portion 10 for the reception of a stamped spring-retaining cap 11 formed of heavy sheet metal and secured in position by a plurality of cap screws 12. The use of a hole drilled entirely through the die member 1 and provided with a removable cap not only facilitates the formation of perfectly aligned holes in the two die members but also simplifies assembly and removal of the die springs.

In accordance with the present invention, each die spring 13, only one of which is illustrated in the drawings, is positioned within a telescopic cylindrical housing, best shown in Figures 1 and 2, and formed of a pair of telescopic tubular elements 13 and 14. The outer extremity of the inner tube element 15 is flanged inwardly at 16 to form a seating surface for the end of the spring 13, and a separate end stamping 17 is brazed, soldered or otherwise fixed to the outer extremity of the element 15 to form a radially projecting flange or rim which fits the walls of the recess 8 and thus aligns the telescopic housing with the axis of the recess. The inner extremity of the inner element 15 is flared outwardly at 18 to form an enlarged guiding rim which fits the inner wall of the outer tubular element 14. The inner end of the outer tube element 14 is spun or otherwise contracted inwardly at 19 to have a sliding fit upon the tube 15. The inwardly projecting portion 19 on the outer element and the outwardly spun rim 18 on the inner element prevent separation of the two telescopic elements in one direction while the outward rim or flange 17, which is secured to the inner tube after the two tube elements are assembled, prevents separation in the other direction of movement. The outer extremity of the outer element is provided with an outw-ardly extending flange 20 which is adapted to seat upon the shoulder 21 formed by the enlarged counterbore 10.

The flange 20, being clamped between the cap 11 and the surface 21, prevents relative movement between the outer tube element 14 and the bore 9; and the spring 13, by engagement with the inturned flange 16 on the inner tube element 15 holds the inner tube against displacement with respect to the die member 2.

The form of housing shown in Figures 1, 2 and 3 is constructed for use with'die elements in which the recess 8, after being formed by drilling operation, has been machined to a flat-bottomed surface in order to form a level seat for the spring. This procedure, while quite expensive, has been followed in the past to avoid subjecting the spring to excessive distortion or load.

In the form of invention shown in Figure 4, the spring housing and remaining portions of a mechanism are the same except that the bottom of the recess 8' in die member 2' is formed solely by drilling operation with the result that the recess has a conical bottom conforming to the tip of the drill, and the outer extremity of the inner tubular element 15 is provided with a stamped end piece 22 of heavy sheet metal which is shaped to have a conical bottom surface 23 which will seat and center the housing on the conical bottom of the recess 8'. The end piece 22 is also shaped to have an annular surface 24 lying in a plane perpendicular to the axis of the recess 8' which serves to sustain the thrust exerted by the spring 13'. The outer extremity of the inner tubular element 15' may, if desired, be flanged inwardly at 16 to form the spring seat, but this construction is optional since the spring can seat directly upon the surface 24 of the end piece 22. The outer periphery of the end piece 22 need not have an accurate fit with the side walls of the recess 8' since the conical end surface 23 will accurately align the housing with respect to the axis of the recess. The form of construction shown in Figure 4 avoids the necessity of machining flat bottoms on the recess and thus materially decreases the cost of die manufacture.

With either form of the invention, the telescopic housing entirely encloses the die spring and thus, in the event of spring breakage, retains spring fragments and prevents them from finding their way into the space between the confronting faces of the die members 1 and 2 where they can cause damage. Since the housing is telescopic, it can elongate as the die members separate and thus accommodates the greater spring length. The outwardly projecting flange 17 in Figure 3 or the conical end piece in Figure 4 engages the side and bottom walls, respectively, of the recess and aligns the axis of the spring with the axis of the recess, thus preventing cocking and consequent overstressing of the spring.

What is claimed is:

l. A spring housing for enclosing a spring which is to be mounted in cylindrical aligned recesses formed in relatively movable die members, comprising a pair of telescopic tubular elements slidably engaged with each other in axial alignment and overlapping for a portion of the length of each, means adjacent the outer extremity of the inner element projecting radially outwardly from the wall of the element for engaging the side wall of a recess in one die member and centering the aXis of the element with respect to the axis of the recess, means on the outer extremity of the inner member projecting radially inwardly from the wall of such member and forming a spring seating surface, and radially outwardly projecting means on the outer end of the outer element adapted to seat on a shoulder formed in the other die member to limit movement of the outer element relative to said other die member in a direction toward the inner element, the outer end of the outer element being open to permit insertion of a spring.

2. In a die mechanism, a pair of relatively movable die members having surfaces positioned face to face, axially aligned cylindrical recesses formed in the faces of said members, one of said recesses passing entirely through one of said members and the other rewss terminating within the body of the other member, a telescopic tubular housing formed of a plurality of telescoped tubes and fitted in said aligned recesses, one of said tubes being positioned at least in part in said one member and having at its outer extremity a flange seated against a surface on said one member which limits movement of said one tube relative to said one member in a direction toward the other member, a helical spring positioned within said tubular housing, means on the tubular housing at its extremity opposite to said flange and forming a seat for one end of the spring, and a retaining cap secured to said one member over the outer end of the recess therein for retaining the spring and housing within said recess.

3. In a die mechanism, a pair of relatively movable die members having surfaces positioned face to face, axially aligned cylindrical recesses formed in the faces of said members, one of said recesses passing entirely through one of said members and the other recess terminating within the body of the other member, a telescopic tubular housing formed of a plurality of telescoped tubes and fitted in said aligned recesses, one of said tubes being positioned at least in part in said one member and having at its outer extremity a flange seated against a surface on said one member which limits movement of said one tube relative to said one member in a direction toward the other member, a helical spring positioned within said tubular housing, means on the tubular housing at its extremity opposite to said flange and forming a seat for one end of the spring, and a retaining cap secured to said one member over the outer end of the recess therein for retaining the spring and housing within said recess, said recess in the other member being a blind drilled hole having a conical bottom, and means on said opposite extremity of said housing defining a mating conical surface adapted to engage the conical bottom of said recess.

4. A spring housing for enclosing a spring which is to be mounted in cylindrical aligned recesses formed in relatively movable die members, comprising a pair of telescopic tubular elements slid-ably engaged with each other in axial alignment and overlapping for a portion of the length of each, means on the outer extremity of the inner member having a conical outer surface portion adapted to seat in the conical bottom of a drilled hole in one die member and having an inner surface lying in a plane perpendicular to the axis of the housing for sustaining the thrust of a spring positioned within the housing, and radially outwardly projecting means on the outer end of the outer element adapted to seat on a shoulder formed in the other die member to limit movement of the outer element relative to said other die member in a direction toward the inner element, the outer end of the outer element being open to permit insertion of a spring.

References Cited in the file of this patent UNITED STATES PATENTS 1,802,552 Corcoran Apr. 28, 1931 2,357,436 Tewksbury Sept. 5, 1944 2,579,641 Aldrich Dec. 25, 1951 FOREIGN PATENTS 580,094 Great Britain Aug. 27, 1946 

